This invention relates to a sprayer which is designed to suck a liquid received in a container into a cylinder by the slide of a piston and spray the liquid under pressure.
With this type of sprayer, the pressing force of a piston and the speed at which the piston is let to fall exert a prominent effect on the condition in which a liquid is sprayed. Where the piston has an insufficient pressing force or is brought down at a low speed, then, a satisfactory spray can not be realized due to a liquid being scattered in coarse particles, droplets, or bar-like form. Further, under the above-mentioned undesirable condition, the same event arises due to pressure drop also when the spraying operation is brought to an end.
For elimination of such drawbacks, there have hitherto been proposed a variety of pressure accumulating type sprayers, which are designed to accumulate a pressing force derived from the descent of a piston in the form of the urging force of compression spring, and, when the urging force exceeds the prescribed level, to open a secondary valve, thereby spraying a highly pressurized liquid. The known sprayers of the above-mentioned type include, for example, an atomizing pump set forth in U.S. Pat. No. 3,399,836 allowed to Fred Pechstein. Fred Pechstein's atomizing pump comprises a cylinder of a larger diameter in which a piston is slidably received and a cylinder of a smaller diameter in which a plunger or valve rod is slidably received, both cylinders being arranged in series. With the atomizing pump of the U.S. Patent, a piston is brought down to pressurize a liquid. When the pressurized liquid is permitted to flow from the cylinder of the larger diameter into that of the smaller diameter, a valve rod falls at a higher speed than that at which the piston is brought down. Thus, the pressurized liquid is sprayed when a secondary valve is opened. A pressure accumulating spring is received in the cylinder of the smaller diameter behind the valve rod so as to be actuated against the force with which the valve rods descends. Many of the prior art pressure accumulating type sprayers utilize the technical concept of the above-mentioned Fred Pechstein's atomizing pump. However, the conventional sprayers based on Fred Pechstein's technical concept are inevitably accompanied with the drawbacks that since the pressurization of a liquid is effected by causing the piston to slide through the cylinder of the larger diameter to apply pressure to the valve rod received in the cylinder of the smaller diameter, the valve rod receives a lower pressure than the pressing force of the piston, failing to allow the pressure accumulate spring to accumulating a sufficiently high pressure. Since the pressure accumulating spring is disposed in a chamber of a smaller diameter, a spring having a large capacity of accumulating pressure can not be utilized for accumulation of pressure. The spray of a liquid can not be commenced at a high pressure and the liquid fails to be sprayed at a fully high pressure, because the pressure accumulating spring does not apply a sufficiently high pressure to the liquid while it is being sprayed.
It is therefore an object of this invention to provide a novel sprayer based on a technical concept entirely different from that of Fred Pechstein and which always enables a liquid to be sprayed under good condition.